Method of precipitating aluminum hydrate.



R. S. SHERWIN.

METHOD OF PRECIPITATING ALUMINUM HYDRATE.

APPLICATION FILED JULY 16,1913.

Patented Dec. 25, 1917.

I 32 mu q/vibmz o:

UNITED STATES PATENT OFFICE.

RALPH S. SHERWIN, OF EAST ST. LOUIS, ILLINOIS, ASSIGNOR TO ALUMINUMCOMPANY OF AMERICA, 01 PITTSBURGH, PENNSYLVANIA, A CORPORATION OFPENNSYL- VAN IA.

METHOD OF PRECIPITATING ALUMINUM HYDBATE.

Patented Dec. 25,1917.

Application filed July is, 1913. Serial No. 779,327.

To all whom it may concern:

Be it known that RALPH S. SHERWIN residing at East St. Louis, county ofSt. Clair, and State of Illinois, have invented certain new and usefulImprovements in Methods of Precipitating Aluminum Hydrate, of

which the following is a full, clear, and exact description.

The invention which constitutes the subject-matter of this applicationrelates to an improved method of precipitating aluminum hydrate.

One of the methods now in vogue in the precipitation of aluminum hydratefrom the solution commonly known in the art as sodium aluminate liquor,consists in establishing a column of the liquor from which the hydrateis to be precipitated and in which is contained a quantity ofprecipitated hydrate in the form of particles, withdrawing precipitatedhydrate from the lower part of the column and returning it to the upperpart thereof, and continuing such withdrawaland return of hydrate whilemaintaining the column free from violent agitation, whereby theprecipitate collects in the lower portion of the column and is withdrawntherefrom with a minimum quantity of the liquor. The older methodpractised.

consists, inter alia, in subjecting the liquor to agitation, more orless violent, byv means of paddles, beaters, or similar devices workingin the liquor, the prevalent belief being that more or less violentagitation was essential to accomplish the precipitation of the hydrate.

The method herein described is an improvement upon the prior methods inthat it effects the precipitation of more aluminum hydrate from theliquor, in the same interval of time. The reactions in the liquor are accompanied by the liberation of considerable heat and as a result, thetemperature of the liguor may reach a point where it seriously a ectsthe rate of precipitation, especially in large units, in which theradiating surface of the apparatus is less in proportion to the cubiccontents of the tank. Consequently, the precipitation of aluminumhydrate in large containers may be carried on more economically if thealuminate liquor be subjected to a cooling process while undergoing suchprecipitation; Availing myself of this fact, I have been led to devisemy present invention, which has for its chief aluminate liquorcontaining solid matter in suspension.

In practising my method in the preferred manner the necessary suspensionof the particles in the column of liquor may be efiected in the usualway. The precipitate is then frequently or continuously withdrawn fromthe bottom of the tank in which the precipitation occurs, exposed to acooling action preferably by contact with the atmospheric air, anddelivered to the column of liquor at or near the top in the formof athin sheet or fine spray, whereby the same is cooled as it falls from asuitable sprayer or rose as a saucer to the said column of liquor. Oneof the great difficulties encountered in reintroducing the precipitatedliquor at the top of the tank, resides in the fact that owing to theviscous properties of the liquor the same would foam and spill over-theupper edge of the tank. To minimize this foaming of the liquor,according to the present practice, some of the liquor containingprecipitated hydrate withdrawn from the bottom of the tank is dischargedat the uphowever, that by reintroducing the liquor containingprecipitated hydrate above the upper surface of the column of liquorwhile such reintroduced portion is in a disintegrated form, that is tosay, in the'form of a fine s ray, or in theform of a thin sheet, this diculty of foaming is completely overcome. I have also found that bybreaking up the stream which discharges into the column of liquor, intominute particles whereby the same is exposed to the atmospheric air, acooling of the liquor containing precipitated hydrate takes place, whichhastens to a maximum the precipitation of the aluminum hydrate from theliquor in the precipitator. One. of the many forms of apparatus by whichthe method may be ractised is illustrated in the accompanying rawings,Figure 1 being a longitudinal vertical section of the precipitating tankwith the cooler secured to the upper end thereof, Fig. 2 being a detailview of the distributer. The vertical cylindrical tank A, which containsthe sodium aluminate liquor, is provided with a conical or hopper bottomto sary) of the liquor passing up the pipe E 7 per edge of theprecipitator.

may be discharged into the column at or adjacent the upper surfacethereof, as shown.

Beyond the branch pipe G I employ a' valve I whereby the flow of liquortothe cooler may be also controlled. A metal distributing saucer L, ofsuitable size and with the walls thereof at the proper angle, is set atthe discharge end of the pipe so as to receive the liquor containingsolid matter in suspension and to cause it to spread on all sides in athin sheet which breaks into fine particles as it falls. A tower M,supported by I- beams N, of cylindrical or other suitable contour,according to the shape of the tank on which the apparatus is used, andwith a diameter less than that of the precipitating tank, prevents theliquor discharged from the cup L from being thrown over the up- Betweenthe top of the precipitator and the bottom of the tower or cylinder, Iprovide a space to allow the air to enter and pass upwardly through thecylinder to cool the liquor discharged from the circulating pipe. Thesaucer which receives and spreads the liquor must be high enough abovethe upper surface of the column in the precipitators to cause the liquordischarged into said saucer to break up into fine particles beforefalling into the precipitator. If the saucer is set too close to thesurface of the liquor, or if for any reason the stream of liquor doesnot break up sufiiciently, it will cause the liquor in the tank to foamand run over the sides of the-precipitator. The size and shape of thesaucer L is such as to give the best 'and most uniform distribution ofthe liquor within the area inclosed by the tower, and

the amount of liquor passing through the pipe E and saucer L may bevaried by means of the valve I according to the rate of cooling desired,as the principle of regulating the spray depends on the fact that thedistance which the liquor will be thrown from the saucer varies with thevelocity.

with which the liquor impinges on the saucer. In order, however, todecrease the velocity at which the liquor impinges upon the-saucer L, Iemploy a pipe 0 whose internal diameter is greater than the horizontalportion of the branch pipe G, it being understood that the elbow F is ofsubstanis enough distance. between the spraying means and the surface ofthe liquor to allow the air bubbles to escape before the falling liquorstrikes the main body of liquor in the.

tank and to the fact that by introducing the falling liquor in theformof a fine spray no air particles are entrapped at the surface of thecolumn and dragged into the same as would be the case if the same wereintroduced in the form of streams.

While the method is described in connection with and is admirablyadapted for the cooling of sodium aluminate liquor during theprecipitation of alumina, it is to be understood that the invention isnot limited to this particular use as the same is obviously applicableto the cooling of any liquor carrying solid matter and which issulficiently viscous to entrain, as the same falls into the main body ofliquor, an aggregation of air particles whichrises to the surface of theliquid as foam.

What claim is 1. The herein described methods of precipitating aluminumhydrate from an alkali aluminate solution, which consists in maintainingan amount of precipitated aluminum hydrate in suspension in' a body ofsaid aluminate solution, withdrawing more or less of the aluminumhydrate from the bottom of the column and reintroducing the same at thetop thereof in the form of a thin sheet of spray exposed to theatmospheric air.

2. The herein described method of precipitating aluminum hydrate from analkali al'uminate solution, which consists in maintaining an amount ofprecipitated aluminum hydrate in suspension in a body of said aluminatesolution, withdrawing more or less of the aluminum hydrate from thebottom of the column, then cooling and reintroducing the same at the topof said column 4. The'method of cooling an alkaline aluminate solutioncontaining particles of aluminum hydrate in suspension, which consistsin withdrawing the said solution from.

the container and re-introducing the same in a disintegrated formthrough a column of am 5. The method of reventing foaming of a viscoussolution w ich consists in withdrawing it from a body thereof andintroducing 1t through a column of air into a container in the form offine particles.

6. The process of precipitating aluminum hydrate from an alkalialuminate solution, said' process comprising the step of breaking up thesaid solution into the form of a fine spray and passing the same initsdisintegrated form through a column. of air, whereby the same may bereintroduced in a column of liquor while avoiding the foaming of thesame.

7. The process of precipitating'aluminum hydrate .from an alkalialuminate solution,

said process comprising the steps of withdrawing the liquor carryingsuspended aluminum hydrate from a body thereof in a container, passingthe same through a cooling medium and reintroducing the same into thebody of liquor in the container in the form of a fine spray.

8. The process of precipitating aluminum hydrate from an alkalialuminate solution, said process comprising the steps of maintaining acolumn of the aluminate solution containing a quantit of precipitatedaluminum hydrate, with rawmg the aluminum hydrate from the bottomof thecolumn, passing the same through a column of air, and reintroducing thesame into the column of liquor in a. disintegrated form, whereby coolingis effected and the particles of the precipltate come into intimatecontact with substantially all portions of the aluminate liquor.

9. A method of precipitating alumin from an alkali aluminatesolutioncomprising the steps of maintaining a column of substantiallyquiescent aluminate solutioncontaining a quantity of precipitatedaluminum hydrate, withdrawlng the aluminum hydrate from the bottom ofthe column, cooling the same by passingit through a column of air andreintroducing it in disintegrated form at the top of the li uor column,whereby cooling is effected and in settling through the liquor theparticles of the precipitate come into intimate contact withsubstantially all portions of the aluminate liquor. V

10. The process of precipitating aluminum hydrate from an alkalialuminate solution, said process'comprising the steps of withdrawin theliquor while carrying some precipitate rom a container, exposing thesame to the atmospheric air under conditions capable of cooling thesame, and reintroducing the same into the body of liquor in thecontainer in the form of a fine spray.

11. The method of accelerating the precipitation of aluminum hydrate,which consists in cooling the solution by withdrawing a quantity of itfrom a body thereof and introducing it through a column of air into acontainer and breaking up saidfalling liquor in the form of fineparticles.

12. The method of reventing foamin of a viscous solution w ich conslstsin w1thdrawing it from a body thereof and introducing it through acolumn of air directly into a container in the form of fine particles.

13. The method of reventing foaming of a viscous liquid which is beingdischarged into a contalner'which consists in effecting said dischargethrough a column of air into the container in the form of fineparticles.

'14. The method of accelerating the precipitation of aluminum hydrateand of-preventing the foaming of liquids containing the same, whichconsists in cooling the solution by withdrawing a quantity of it from abody thereof and introducing it" throu h a column ofair into a containerand brea ing up said falling liquor into the form of fine particles.

15. The herein described process of withdrawing heat from a body of,aliquor possessing a relatively great tendency to foam which compriseswithdrawing an amount of such liquor from such body, and by forming thesame into a spray, at a point so far above suchbody of li uor that whenthe spray enters the body 0 liquor it will be in t e'form of small dropswhereby no air bubbles will be carried into said liquor, and no foamproduced.

16. A process of precipitating aluminum hydroxid from alkali aluminatesolution which comprises maintaining a body of aluminate solutioncontaining aluminum hydrate, distributed therethrough, withdrawing fromthe lower part of said body a stream of said liquid with suspendedaluminum hydrate, reintroducing the liquid so withdrawn, at the upperpart ofsaid body, and coolin the. withdrawn portion at a suitable pomtin its travel.

17. In the precipitation of aluminum hydroxid from a solution of alkalialuminate by maintaining precipitated aluminum hydroxid in contact withand distributed throughout the body of said liquor, the stepofwithdrawing from the lower part of said body of such liquor, a ortionof liquor carrying precipitate, an deliverin the same, through a columnof air in a dlsenteof such liquid from a body thereof, and in- Intestimony whereof I afiix my signature troducing the same, in the formof fine parin the presence of two subscribing Witnesses. ticles, at a,point sufficiently above the surface of such body of liquor, that suchin- RALPH SHERWIN' troduced portion renters the said body of Witnesses:liquor, as fine drops, and without carrying (1E. HODGSON,

air into said body of liquor. H. P. I-Irzmrmn.

